1. Field of the Invention
This invention relates generally to the field of integrated circuit manufacturing and, more particularly, to a method for monitoring processing variations in sputtered metallic films.
2. Description of the Related Art
For many years, metal sputtering has been used to form films on semiconductor wafers. Although sputtering is generally regarded as a cost effective way to deposit metal on a semiconductor wafer, sputtering techniques have suffered from technical drawbacks in the Ultra-Large-Scale-Integration (ULSI) era. Most significantly, it is becoming increasingly difficult to sputter metals into contact holes. The aspect ratio of a contact hole is determined by dividing the contact hole""s height by its diameter. In the ULSI era, aspect ratios of contact holes are growing larger as the diameters shrink. As a result, it has become increasingly more difficult to sputter metals, such as titanium, into the bottom of the contact holes. Inadequate metal formation at the bottom of a contact hole produces a contact with an undesirably high resistance.
A collimated sputtering process has been used to achieve better uniformity at the bottom of contact holes because such a process directs the deposited metal in a substantially perpendicular manner onto the surface of the wafer. In a collimated sputtering process, a collimator is placed between a metal target and a wafer. The collimator contains holes through which liberated atoms from the metal target must pass to reach the wafer. Atoms having trajectories substantially perpendicular to the wafer pass through the collimator, while atoms having undesired trajectories accumulate on the walls of the collimator.
While collimation provides for contacts with better coverage at the bottom of the contact holes, the technique does suffer from the drawback that the inside walls of the collimator become coated with the metal atoms. Over time, the build-up on the walls changes the effective trajectory of the atoms that are able to proceed to the wafer surface and affects the profile of the metal film so deposited. Once this build-up becomes severe, the collimator is cleaned or changed. However, there is no method or apparatus to monitor the status of the collimator to determine when to clean or change it.
The present invention is directed to overcoming, or at least reducing the affect of, one or more of the problems set forth above.
In accordance with one aspect of the present invention there is provided a method for fabricating a monitor for monitoring processing variations of a conductive material. The method includes the steps of: (a) forming a plurality of trenches on a substrate; (b) disposing a conductive material into the plurality of trenches; (c) placing two terminals in contact with the conducting material; and (d) coupling the two terminals to a resistance measuring device.
In accordance with another aspect of the present invention, there is provided a method for monitoring step coverage of a conductive material. A substrate having a plurality of trenches is placed in a deposition chamber. A conductive material is disposed into the plurality of trenches. Two terminals are placed in contact with the conductive material. A resistance is measured between the two terminals.
In accordance with a further aspect of the present invention, there is provided a method for monitoring step coverage of a conductive material to be deposited onto a production wafer containing contact holes having a given aspect ratio. The production wafer is placed into a deposition chamber. A test wafer having a plurality of trenches is placed into the deposition chamber. The trenches have an aspect ratio similar to the aspect ratio of the contact holes. Conductive material is disposed into the trenches. Two terminals are coupled to the conductive material, and a resistance is measured between the two terminals.
In accordance with yet another aspect of the present invention, there is provided an apparatus for monitoring processing variations of a conductive material relative to a given feature. The apparatus includes a substrate having a plurality of parallel trenches. The trenches have an aspect ratio correlative to a given aspect ratio of the given feature.
In accordance with still another aspect of the present invention, there is provided an apparatus for monitoring processing variations of a conductive material relative to a given feature. The apparatus includes a substrate having a plurality of parallel trenches. The trenches have an aspect ratio correlative to a given aspect ratio of the given feature. The trenches have a conductive material disposed therein. Two terminals are coupled to the conductive material.
In accordance with a still further aspect of the present invention, there is provided an apparatus for monitoring processing variations of a conductive material relative to a given feature. The apparatus includes a substrate having a plurality of parallel trenches. The trenches have an aspect ratio correlative to a given aspect ratio of the given feature. A conductive material is disposed in the trenches. Two terminals are coupled to the conductive material, and a resistance measuring device is coupled to the two terminals.